This invention relates to a disposable diaper adapted to absorb and to hold excretion discharged thereon.
Japanese Patent Application Publication No. 1999-113958A describes a disposable diaper basically comprising a panel structure which comprises, in turn, a liquid-pervious topsheet, a liquid-impervious backsheet and a liquid-absorbent core disposed between these two sheets, and a sheet member lying above the topsheet. The panel structure is longitudinally composed of a front waist region, a rear waist region and a crotch region extending between these waist regions wherein a pair of side flaps extend in a longitudinal direction immediately outside transversely opposite side edges of the core and a pair of end flaps extend in a transverse direction immediately outside longitudinally opposite ends of the core. The sheet member comprises a pair of side walls extending in the longitudinal direction in the vicinity of the transversely opposite side edges of the core and a top wall extending between top edges of the respective side walls in parallel to the top- and backsheets.
The respective side walls have the side edge portions thereof bonded to the vicinity of the side edges of the core in the panel structure and the longitudinal opposite ends thereof bonded to the end flaps of the panel structure. The top wall has an opening at a location corresponding to a middle zone of the crotch region and longitudinally opposite end portions bonded to the end flaps. This diaper of prior art enables the respective side walls to rise above the panel structure and enables the top wall to be spaced upward from the panel structure so that a cavity adapted to receive excretion discharged on the diaper may be defined between the panel structure and the sheet member as the top wall is spaced upward from the panel structure.
The top wall of the sheet member is of a rectangular shape transversely dimensioned to be smaller than a transverse dimension of the panel structure and not present above the side flaps of the panel structure. The side walls of the sheet member are bonded to the panel structure except its end flaps only along the side edge portions of the side walls. As a result, the sheet member is not restricted by the panel structure and freely movable.
In the case of the diaper disclosed by above-identified Publication, the top wall comes in contact with wearer""s belly and hip merely over a small area in the front and rear waist regions of the diaper as the diaper is put on the wearer""s body and the sheet member is movable independently of the panel structure. Consequently, the sheet member often shifts particularly in the transverse direction in the front and rear waist regions. Such transverse shift of the sheet member may lead to a problem that the opening formed in the top wall may miss the extent of the wearer""s urinary organs and/or anus and be unable to receive excretion into the cavity.
It is an object of this invention to provide a disposable diaper improved so that the top wall of the sheet member may come in close contact with a wearer""s belly and hip over a relatively large area and the sheet member may be sufficiently prevented from shifting sideways in the front and rear waist regions to receive excretion reliably into the cavity.
According to this invention, there is provided a disposable diaper comprising: a panel structure including a liquid-impervious base sheet and a liquid-absorbent core attached thereto and a sheet member extending above the panel structure; the panel structure having a front waist region, a rear waist region and a crotch region extending between these waist regions and including a pair of first side flaps extending in the longitudinal direction immediately outside transversely opposite side edges of the core and a pair of end flaps extending in a transverse direction immediately outside longitudinally opposite ends of the core; the sheet member including a pair of side walls extending in the longitudinal direction in the vicinity of the transversely opposite side edges of the core so that the side walls are normally biased to rise above the panel structure and a top wall extending between top edges of the side walls in parallel to the base sheet so that the top wall is normally biased to be spaced apart from upward from the panel structure; the side walls respectively comprising side edge portions bonded to the core in the vicinity of the transversely opposite side edges thereof and first end portions bonded to the end flaps; the top wall having at least one opening defined between the side walls and second end portions bonded to the end flaps so that a cavity adapted to receive excretion is defined between the panel structure and the sheet member.
According to this invention, the top wall has a pair of second side flaps extending immediately outside the top edges of the side walls in parallel to the first side flaps so that the first side flap and the second side flap are bonded together at least along the transversely opposite side edge portions of the first and second side flaps overlapping each other in the front and rear waist regions.
According to one embodiment of this invention, at least the top wall of the sheet member is elastically stretchable at least in the longitudinal direction of the longitudinal and transverse directions and bonded under tension in the longitudinal direction to the panel structure so that the side walls may be normally biased to rise above the base sheet and the top wall may be normally biased to be spaced apart from the base sheet.
According to another embodiment of this invention, the first and second side flaps have transversely opposite side edges thereof curving inward in the transverse direction in the crotch region so as to describe circular arcs so that the top wall has a transverse dimension in the crotch region smaller than the corresponding dimension in the panel structure.